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Jacobs Ladder

Discussion in 'Electronic Basics' started by Michael, Oct 25, 2006.

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  1. Michael

    Michael Guest


    I hope you don't mind me posting this here as I guess technically it's not

    I'm in the UK and would like to make a Jacobs ladder using a neon sign
    transformer. Firstly does anyone here have a suitable transformer that I
    could use? And secondly if I can't find a UK one, can use a US one as long
    as I step down the voltage to the 110V?


  2. Chris

    Chris Guest

    Hi, Michael. You should be able to find one for a few pounds at a junk
    shop -- call around.

    Take a look at this link before you start:

    Sam Goldwasser offers a lot of good advice here. Be sure you include a
    fuse on the primary, and also a "dead man's switch" on the primary
    (basically a big pushbutton capable of switching several amps that only
    makes contact when it's pushed down). Safety first.

    This link also shows the electrode you can base at the bottom of the
    ladder to make spark ignition easy. Be sure to use at least 2 ea. 2
    watt 1 megohm resistors in series with the electrode -- the more, the
    merrier. If you can use 4 ea. 470K, or even 6 ea. 330K resistors, all
    the better. You want to avoid having the resistors arc over.

    Here's the schematic, stolen shamelessly from Mr. Goldwasser (view in
    fixed font or M$ Notepad):

    | \ /
    | \ /
    | \ /
    | \ /
    | T \ /
    | Line --- _ / | \
    | o----o o--o_/ \o---. ,----------------/ | \-------.
    | )||( HV .-. |
    | )||( | |1M 2W |
    | )||( | | |
    | )||,-------. '-' |
    | )||( CT | | |
    | )||( | .-. |
    | Neutral )||( | | |1M 2W |
    | o------------------'| '-------)-----. | | |
    | | HV | | '-' |
    | | | | | |
    | | | '-----o----------'
    | | |
    | GND | |
    | o-------------------o---------'
    (created by AACircuit v1.28.6 beta 04/19/05

    Follow all the precautions in both articles. If you don't understand
    what you're doing, ask.

    Good luck, and play safe
  3. Nice post on the subject. I built mine when about 14 yrs old, using
    the HV lead (pulled out of the side of the display tube) from a TV
    flyback output. In fact, I just left the TV as a whole unit and just
    let it run without the HV and used bent hanger wire for the ladder.

    It worked. It was NOT safe. I don't recommend the procedure. But
    there it is. And I'm glad there is the internet today to discuss
    these things in a context that helps improve safety and still to get a
    chance to have fun, too.

  4. I do want to add:

    1. By-and-large, neon sign transformers have a high (but maybe short of
    100%) tendency to be better than flyback transformers for this.

    2. Make sure the wires are adequately thick (typically in ballpark of a
    couple mm wide or more)

    3. Make sure the wires diverge sufficiently gently. I have heard a bit
    (can't attribute) maximum divergence of 11 degrees with a "traditional"
    neon sign transformer. I would advise go no more than half that -
    preferably not exceed 5 degrees until you see really stromg evidence of
    your arrrangement adequately reliably working with and larger angle of

    4. Have no sharp bends in wires that the arc has to climb over - the arc
    may stall in a sharp transition from wires diverging by 1 degree to wires
    diverging by 6 degrees even if the arc can climb through a gently curved
    transition from vertical to 98 degrees of divergence!

    5. Oil burner transformers come with some recommendations, some
    favorable! One of mine is to operate them no more than 15, possibly 20
    minutes per hour! They are much more compact than neon sign transformers,
    but that comes with expense of them *NOT* being good for continuous

    6. "Electronic neon sign transformers" I get a few complaints about when
    used for alternative purposes that "old tech" neon sign transformers have
    a good track record of being good for!

    7. Fatality rate from a power-line-frequency AC shock exceeds zero at 30
    milliamps or somewhat less, despite the main electric shock fatality mode
    having wide citation of being high for current in a range of 100 mA to 1
    Electrocution is so unreliable that "The Electric Chair" relies on eith
    cooking (burning) vital organs, or paralyzing breathing muscles long
    enough to get the brain so oxygen-starved as to be unable to resume
    activation of breathing after the jolt ends. I expect lack of
    electrocution from more moderate shocks (with current on the other side of
    the peak of achievement of electrocution via the mode that electrocution
    usually occurs) to be similarly unreliable.

    - Don Klipstein ()
  5. I used to have a really nice sign transformer with large, glass stand
    offs at either side of the long-ways ends and with through-bolts that
    worked well. Long gone, now. But it really was nice for this kind of
    thing. Weighed.. probably 6 pounds or so. Had mounting lugs on the
    bottom. Was about 12"x8"x6" in size, if memory serves.
    Yes. I used hanger wire at the time. Darned things are mostly just
    plastic, these days. But back then, you could get uncoated wire types
    you didn't need to scrape to make work okay.
    I had to play with that. It's about the heated, ionized air rising, I
    believe. I had problems if there was a gust of wind, things like

    I did not do this myself, and I wish I had tried it now, but I saw a
    jacobs ladder with acrylic sheets front and back side to contain the
    region against wind and to aid the process. Worked really well.
    Agreed, completely. I spent time making things very straight, after
    learning all this from seeing.
    Interesting point.
    I was 'hit' more than once by the 25kV from the back of a color TV set
    and by my jacobs ladder, too. Luckily (or not, perhaps), I don't
    really remember what it felt like so much, anymore. Just vaguely.
    It's not something I'd take silly chances with, today, though I'm
    still very capable of making stupid mistakes.

  6. That won't kill you. A sign transformer or an oil burner ignition system
    will. Very dead.
  7. Ah. Good thing as a kid I only used the TV flyback and couldn't get
    my hands on any sign transformers at the time, then. Must be why I'm
    still here.

  8. Michael

    Michael Guest

    Thanks guys.

    I'm planning on using the coathanger (got some in the wardrobe) idea and
    setting the whole thing in an clear acrylic tube about 100mm diameter. That
    way i'll not only get a 'better' effect as they'll be no wind etc but its
    also alot safer should it fall over.

    Still not sure what to do about the transformer though. Can't seem to get
    any old ones and don't really want to buy a new one. Are there any 'other'
    things I could do with it that could persuade me to part with the money?
    £60GBP seems alot from just one experiment.......

    The other thing is that apparently you can use a CRT monitor or a ignition
    coil from a car. Though I don't think I'll get as good results by using

  9. Baron

    Baron Guest

    You could always wind your own transformer ! I've seen 100Kv+ produced
    from home made ones. There is a web site dealing with "High voltage"
    Can't remember the URL ! Maybe someone will chip in with it.
  10. Baron

    Baron Guest

    Minute I hit send.... then I remember it !
  11. I've had my share of thumps - one left me deaf for 20 minutes - but those
    things are very dangerous indeed.
  12. Actually, usually not! Problem is, only usually!

    - Don Klipstein ()
  13. Whew! That means I might have _still_ survived my childhood had I
    happened up one. That's a relief!! ;)

  14. Some people survive dynamite. Not a good bet.
  15. I survived my nitroglycerin phase, my mercury fulminate phase, my
    shooting at 5 pound tubes of white phosphorus metal floating in the
    lake to watch them blow up phase, my various rocket fuel in steel
    casings launched from behind sand bags phase (yes, some blew up), my
    picric acid and potassium chlorate mixture in the rifle shells with
    lit fuses shot from sling shots phase, and my boiling sulfuric acid as
    a double boiler for melting potassium nitrate and sugar phase...

    Oh, I forgot... my fireworks making phase, too.


  16. Don Bruder

    Don Bruder Guest

    I wonder how I survived, having played with both furnace and sign
    Xformers, and being "bit" multiple times by both. Not "fun", by any
    stretch, but it didn't seem very fatal...
  17. Rubber shoes?
  18. Rich Grise

    Rich Grise Guest

    When I was in high school, the physics dept. had an old TV and a scope,
    and they let me play with them. I was curious about the plate waveform
    on the Horiz. output tube, so I went to probe it, and drew about a 1 1/2"
    arc to the scope probe.

    It was a toob-type scope, so naturally it survived, and interestingly, so
    did I. :)

  19. Rich Grise

    Rich Grise Guest

    A toy train transformer and car coil are OK too. ;-)

  20. Rich Grise

    Rich Grise Guest


    When I was in my pre- or early teens, I got 1900V from one hand to
    the other.* I felt it all through my chest, and surprisingly, my
    head, as if the current went from one hand, up my arm, up the
    side of my neck, through my head, down the other side of my neck,
    and out the other hand. {Gee, Rich, is that how you got brain-damaged?
    ha, ha. ;-) ]

    Reversing direction 60 times a second, of course. ;-)

    It was a rush. >:->


    * That's an estimate, really. I had a 100:1 car coil, and a model
    train transformer that was essentially a variac that stopped at
    about 19VAC.
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